Advances in modern electronics require the development of polymer-based
dielectric materials with high dielectric constant, low dielectric loss,
and high thermal stability. Fundamental dielectric theory suggests that
strongly dipolar polymers have the potential to realize a high
dielectric constant. In order to achieve high thermal stability, these
polymers should also possess a high glass transition temperature T-g.
However, it has been observed that in many dielectric polymers the
dielectric constant decreases markedly at temperatures below Tg due to
dipole freezing. This study shows, through combined theoretical and
experimental investigations, that nano-structure engineering of a
weakly-coupled strongly-dipolar polymer can result in a high energy
density polymer with low loss and high operating temperature. Our
studies reveal that disorder creates a significantly larger free volume
at temperatures far below T-g, enabling easier reorientation of dipoles
in response to an electric field in aromatic urea and thiourea polymers.
The net result is a substantial enhancement in the dielectric constant
while preserving low dielectric loss and very high breakdown field.
These results here pave the way for engineering the nanostructure to
create high energy density polymers with low loss and high operating
temperature. (C) 2015 Elsevier Ltd. All rights reserved.